This section provides background information related to the present disclosure which is not necessarily prior art.
It is often desired to power a device with rotary power that is transmitted from a prime mover either directly or through an endless power transmitting element, which could employ a belt, a chain and/or a toothed gear. Such devices could, for example be connected to the engine of a motor vehicle via an accessory drive or a timing drive and could include a pump (e.g., water pump, vacuum pump, power steering pump, air compressor, air conditioning compressor), a means for generating electricity (e.g., alternator, generator, starter-alternator, starter-generator), and/or a fan, for example.
It will be appreciated that in situations when the output of the device is not needed or desired, operation of the device will be associated with reduced efficiency of the prime mover. In an automotive context for example, it may not be necessary to operate the engine water pump when the engine is cold and is being started and as such, the operation of the engine water pump when the engine is cold and being started reduces the overall fuel efficiency of the engine. To overcome this drawback, it was known in the art to provide a clutch to selectively operate the device. Such clutches typically required some sort of power, usually electrical power, to permit rotary power to be transmitted through the clutch to drive the device. More recently, several types of clutches have been developed by Litens Automotive Partnership that can be configured to transmit rotary power to a driven device in a normal or unpowered state and inhibit transmission of rotary power to the driven device in a power state that uses a relatively low-power input.
While such clutches are suitable for their intended purposes, such clutches are nonetheless susceptible to improvement.